Sorry for the necro-bump. I mostly lurk and hardly ever (never) post, but I thought this was worth noting: the Formula 5F6 has been traced! I sent mine over to Robert at PedalPCB, who now sells a PCB. As some might have guessed, the layout is identical to the DLS MKIII- and indeed it uses the same PCB with the same S. Bass & S. Lead designations inside.

great news indeed! Been waiting for this one and tried to build one by ear - The AMZ "Tweed Stack" almost got me in the zone, so at least i guessed right Ordered a PCB from GuitarPCB and BB'd it using the schematic provided there while waiting for the postman. Since it uses MPF4393 which are not readily available here in good old Austria I substituted MPF102 and some of my trusty 2N5457, will try with NTE457, though. As usual the GuitarPro demo video has a killer sound, the "original" ain't - but that's real life I guess.